I would go with the Speedwerx y pipe for the application as they are a big part of the flow of a single pipe. I installed the y pipe before the single and it was the biggest part of the pipe gain. Ran it like that for a while till could afford the Speedwerx pipe. Think it was worth like 3-5 HP, just the y pipe. Factory y pipes are crimped down a TON over the Speedwerx y pipe, you want flow.